Population protocols are a model for parameterized systems in which
a set of identical, anonymous, finite-state processes interact pairwise through rendezvous
synchronization. In each step, the pair of interacting processes is
chosen by a random scheduler.
Angluin et al. (PODS 2004) studied population protocols as a distributed computation model.
They characterized the computational power in the limit
(semi-linear predicates) of a subclass of protocols (the well-specified ones).
However, the modeling power of protocols go beyond computation of semi-linear predicates and they can be used to study a wide range of distributed protocols,
such as asynchronous leader election or consensus, stochastic evolutionary processes, or chemical
reaction networks.
Correspondingly, one is interested in checking specifications on these protocols that go beyond
the well-specified computation of predicates.

We characterize the decidability frontier for the model checking problem for population protocols against
probabilistic linear-time specifications.
We show that the model checking problem is decidable for qualitative objectives, but as hard as the reachability problem for Petri nets.
However, it is undecidable for quantitative properties.
Our decidability proof uses techniques from Petri net theory, and the characterization of limit behaviors of
population protocols.
In particular, our results show decidability of the following basic verification problems:
Is a given protocol well-specified (i.e., computes a predicate in the sense of Angluin et al.)?
Does a protocol compute a given predicate?

[Joint work with Javier Esparza, Pierre Ganty, and Jerome Leroux]

Dates & Times

On Monday, March 7, the meeting starts at 09:00 in the morning. We expect to finish at lunch time on Tuesday, March 8. Especially for those intending to stay on we will provide office space and meeting facilities.

The workshop dinner will take place on Monday, March 7, at the Café am Schloss, commencing at 19:30.

An informal get-together on Sunday evening will take us to the Stiefelbräu at the corner of St. Johanner Markt. We meet there at 19:30 (entrance on Fröschengasse), or at 19:20 at the fountain on St. Johanner Markt.

Getting to Saarbrücken by car

Parking on Campus

If you arrive on Campus by car, use the parking deck "Universität Ost", which is closest to the computer science buildings (see Campus map; you want to park next to the letter E). Draw a normal parking ticket when entering. We will exchange that ticket for a free exit ticket on site.

Getting to Saarbrücken by plane

There are direct connections between Saarbrücken Airport (IATA: SCN) and Berlin Tegel (Air Berlin), Hamburg (Luxair), Luxemburg (Luxair), and Palma de Mallorca (Air Berlin).
There is an hourly bus connection between the airport and the city centre. Getting to Campus will be significantly faster by taxi, though.

The ticket price is 2.60 € for a single bus ride. Tickets can be bought from the driver. The 'Universität Busterminal' stop is reached once you have crossed the entire Campus, between a parking deck (right) and the Fraunhofer-Institut (left). Get off, and walk back some 200 meters to the Campus. Right after the gate, the CS buildings are to your left and right (quiet new).